Marking methods such as roller printing, screen printing, transfer printing, and stitching or sewing of messages have been used for marking textiles such as woven fabrics, non-woven fabrics, and blended woolen fabrics. However, these conventional methods are expensive and slow, because they require special preparation of the fabric and/or additional manufacturing steps. Therefore, these methods are not economical.
The use of ink jet printing has been proposed as a more economical and flexible method. Because ink jet printing could be done "in-line," it would not slow the production process.
Ink jet printing is a well-known technique by which printing is accomplished without contact between the printing device and the substrate on which the printed characters are deposited. Briefly described, ink jet printing involves the technique of projecting a stream of ink droplets to a surface and controlling the flight of the droplets electronically so that they are directed to form the desired printed image on that surface. This technique of non-contact printing is particularly well suited for application of characters onto irregularly shaped surfaces, including, for example, the curved bottom of beverage containers.
In general, an ink jet composition must meet certain rigid requirements to be useful in ink jet printing operations. These relate to viscosity, resistivity, solubility, compatibility of components and wettability of the substrate. Further, the ink must be quick-drying and smear resistant, must be capable of passing through the ink jet nozzle without clogging, and must permit rapid clean-up of the machine components with minimum effort.
Ink jet printing, however, also has several drawbacks. The quality of the print tends to be impaired due to blotting on the cloth, partly because the ink jet printer does not allow the use of an ink having high viscosity and partly because cloth usually has a more uneven texture than paper, thus making it difficult to print patterns of minute or delicate design. In addition, discharge of the ink tends to be unstable, and the response to high frequency is liable to be impaired depending on the physical property of the ink, owing to the fact that the ink has to be discharged through minute nozzles at high velocity and high frequency. Further, print formed using a conventional ink jet formulation exhibits a slow dye-fixing rate and minimal washing fastness.
Certain ink jet formulations and methods of using them have been proposed to eliminate these problems. U.S. Pat. No. 4,702,742 relates to a method of applying an aqueous dye containing an ink on cloth that has been previously treated with an ink acceptor. The ink is then optionally subjected to a dye-fixing treatment.
U.S. Pat. No. 4,725,849 discloses a process of ink jet printing comprising applying an aqueous dye-containing ink to a cloth that has been pre-treated with an ink receiving material having a viscosity of 1000 centipoises. The ink receiving material may be a water soluble resin-containing solution or a hydrophilic resin-containing solution.
U.S. Pat. No. 4,849,770 relates to an ink jet formulation comprising a reactive dye or reactive dispersing dye, and a solvent composed mainly of water and an organic solvent non-reactive with the dye. This formulation is applied via ink jet printing to a textile, and is then subjected to a dye-fixing treatment.
U.S. Pat. No. 4,969,951 discloses an ink jet formulation comprising a reactive disperse dye and a solvent composed of water, or water and a water-soluble organic solvent. This formulation is applied via ink-jet printing to a textile, and is then subjected to a dye-fixing treatment.
Japanese Patent No. 62225577 relates to an ink jet composition for textile printing operations comprising a pigment, a water-soluble or aqueous dispersible polyester or polyamide, a cross-linking agent, and water.
Japanese Patent No. 61213273 discloses an ink jet composition for use with polyester fibers comprising a water-insoluble pigment, dispersant consisting of a 3:1 ratio of aromatic rings to sulfonate or sulphuric ester group.
Japanese Patent No. 62231787 relates to a method of textile printing using an ink jet composition comprising a pigment and a water-soluble or dispersable polyester or polyamide. The textile to be printed is first treated with a metal salt or cationic compound. The ink is then applied, and is cross-linked by a cross-linking agent present either in the ink or on the textile.
Japanese Patent No. 2189373 discloses an ink jet composition for textile printing operations comprising water-insoluble pigment having particles with a diameter of 0.03-1.0 microns, and a dispersion media, wherein the solution density is 1,010-1,300.
The aforementioned ink compositions and methods of using them also suffer from several drawbacks. First, in some instances it is necessary to pre-treat the textile prior to application of the ink to prevent spreading or blotting. Other of the above-noted patents require chemical fixing treatments after the ink has been applied. Further, all of the aforementioned ink formulations and methods relate to dark-colored inks for use on white textiles, or white textiles that are dyed light or pastel colors. These inks are not visible if after the application of the ink, the textile is dyed a dark color, such as navy blue, maroon, or black.
Therefore, to date there has been no white or pastel-colored ink formulation for ink jet printing on textiles that resists dark-colored dyes, so that the message printed with that ink is visible after the fabric is dyed with a dark-colored dye. There exists a need for such inks in the industry. Currently, fabrics are coded with brand names, sizes, or color information after the dying process. This separate step, which is currently accomplished by stitching or contact printing, is inefficient, because it slows down production. If the product coding is obtained through a subsequent dying step, the utility of marking such information is lost. This is a particular problem when fabric, especially hosiery fabric, is subjected to dark dyes.